The pharmacokinetics and pharmacodynamics of propofol in a modified cyclodextrin formulation (Captisol) versus propofol in a lipid formulation (Diprivan): an electroencephalographic and hemodynamic study in a porcine model

How Is the Nociceptive Withdrawal Reflex Influenced by Increasing Doses of Propofol in Pigs?

The nociceptive withdrawal reflex (NWR) is a physiological, polysynaptic spinal reflex occurring in response to noxious stimulations. Continuous NWR threshold (NWRt) tracking has been shown to be possibly useful in the depth of anesthesia assessment. The primary aim of this study was to describe how propofol modulates the NWRt over time in pigs. Five juvenile pigs (anesthetized three times) were included. An intravenous (IV) infusion of propofol (20 mg/kg/h) was started, and boli were administered to effect until intubation. Afterwards, the infusion was increased every ten minutes by 6 mg/kg/h, together with an IV bolus of 0.5 mg/kg, until reaching an electroencephalographic suppression ratio (SR) of between 10% and 30%. The NWRt was continuously monitored. For data analysis, the time span between 15 min following intubation and the end of propofol infusion was considered. Individual durations of propofol administration were divided into five equal time intervals for each pig (TI1-TI5). A linear regression between NWRt and TI was performed for each pig. Moreover, the baseline NWRt and slopes of the linear regression (b1) were compared among days using a Friedman Repeated Measures Analysis of Variance on Ranks. The NWRt always increased with the propofol dose (b1 = 4.71 ± 3.23; mean ± standard deviation). No significant differences were found between the baseline NWRt and the b1 values. Our results suggest that the NWRt may complement the depth of anesthesia assessment in pigs receiving propofol.

How is depth of anaesthesia assessed in experimental pigs? A scoping review

BACKGROUND

Despite the large number of pigs involved in translational studies, no gold standard depth of anaesthesia indicators are available. We undertook a scoping review to investigate and summarize the evidence that sustains or contradicts the use of depth of anaesthesia indicators in this species.

METHODS

Medline, Embase and CAB abstract were searched up to September 22nd 2022. No limits were set for time, language and study type. Only original articles of in vivo studies using pigs or minipigs undergoing general anaesthesia were included. The depth of anaesthesia indicators reported in the selected papers were divided in two categories: A, indicators purposely investigated as method to assess depth of anaesthesia; B, indicators reported but not investigated as method to assess depth of anaesthesia.

RESULTS

Out of 13792 papers found, 105 were included after the screening process. Category A: 17 depth of anaesthesia indicators were found in 19 papers. Studies were conducted using inhalant anaesthetics as the main anaesthetic agent in the majority of the cases (13/19 = 68.4%), while 3/19 (15.8%) used propofol. The most investigated depth of anaesthesia indicators were bispectral index (8/19 = 42.1%) and spectral edge frequency 95% (5/19 = 26.3%). Contrasting results about the specific usefulness of each depth of anaesthesia indicators were reported. Category B: 23 depth of anaesthesia indicators were found in 92 papers. The most reported depth of anaesthesia indicators were: motor response following a stimulus (37/92 = 40.2%), depth of anaesthesia scores (21/92 = 23.3%), bispectral index (16/92 = 17.8%) and spectral edge frequency 95% (9/92 = 9.8%).

CONCLUSION

Results highlight the lack of scientifically valid and reliable indicators to ensure adequate depth of anaesthesia in pigs.

Comparison between continuous rate infusion and target-controlled infusion of propofol in dogs: a randomized clinical trial

OBJECTIVE

To compare a propofol continuous rate infusion (CRI) with a target-controlled infusion (TCI) in dogs.

STUDY DESIGN

Randomized prospective double-blinded clinical study.

ANIMALS

A total of 38 healthy client-owned dogs.

METHODS

Dogs premedicated intramuscularly with acepromazine (0.03 mg kg^-1) and an opioid (pethidine 3 mg kg^-1, morphine 0.2 mg kg^-1 or methadone 0.2 mg kg^-1) were allocated to P-CRI group (propofol 4 mg kg^-1 intravenously followed by CRI at 0.2 mg kg^-1 minute^-1), or P-TCI group [propofol predicted plasma concentration (Cp) of 3.5 μg mL^-1 for induction and maintenance of anaesthesia via TCI]. Plane of anaesthesia, heart rate, respiratory rate, invasive blood pressure, oxygen haemoglobin saturation, end-tidal carbon dioxide and body temperature were monitored by an anaesthetist blinded to the group. Numerical data were analysed by unpaired t test or Mann-Whitney U test, one-way analysis of variance and Dunnett's post hoc test. Categorical data were analysed with Fisher's exact test. Significance was set for p < 0.005.

RESULTS

Overall, propofol induced a significant incidence of relative hypotension (mean arterial pressure 20% below baseline, 45%), apnoea (71%) and haemoglobin desaturation (65%) at induction of anaesthesia, with a higher incidence of hypotension and apnoea in the P-CRI than P-TCI group (68% versus 21%, p = 0.008; 84% versus 58%, p = 0.0151, respectively). Propofol Cp was significantly higher at intubation in the P-CRI than P-TCI group (4.83 versus 3.5 μg mL^-1, p < 0.0001), but decreased during infusion, while Cp remained steady in the P-TCI group. Total propofol administered was similar between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Both techniques provided a smooth induction of anaesthesia but caused a high incidence of side effects. Titration of anaesthesia with TCI caused fewer fluctuations in Cp and lower risk of hypotension compared with CRI.

Physicochemical Characterization and Pharmacological Evaluation of Novel Propofol Micelles with Low-Lipid and Low-Free Propofol

We developed safe and stable mixed polymeric micelles with low lipids and free propofol for intravenous administration, to overcome the biological barrier of the reticuloendothelial system (RES), reduce pain upon injection, and complications of marketed propofol formulation. The propofol-mixed micelles were composed of distearoyl-phosphatidylethanolamine-methoxy-poly (ethylene glycol 2000) (DSPE mPEG2k) and Solutol HS 15 and were optimized using Box Behnken design (BBD). The optimized formulation was evaluated for globule size, zeta potential, loading content, encapsulation efficiency, pain on injection, histological evaluation, hemolysis test, in vivo anesthetic action, and pharmacokinetics, in comparison to the commercialized emulsion Diprivan. The optimized micelle formulation displayed homogenous particle sizes, and the free drug concentration in the micelles was 60.9% lower than that of Diprivan. The paw-lick study demonstrated that propofol-mixed micelles significantly reduced pain symptoms. The anesthetic action of the mixed micelles were similar with the Diprivan. Therefore, we conclude that the novel propofol-mixed micelle reduces injection-site pain and the risk of hyperlipidemia due to the low content of free propofol and low-lipid constituent. It may be a more promising clinical alternative for anesthetic.

Cyclodextrins in Parenteral Formulations

Most drugs have very limited solubility in water and some can be extremely difficult to formulate as parenteral solutions where the dose should preferably be dissolved in couple of ml of aqueous media without use of organic solvents and surface active agents, or application of somewhat extreme techniques such as prodrug formation. Thus, pharmaceutical formulators are constantly looking for new, biologically acceptable, and low-cost armamentarium for parenteral formulation development. Cyclodextrins (CDs) are enabling pharmaceutical excipients that can temporarily camouflage undesirable physiochemical drug properties such as low aqueous solubility through formation of drug/CD inclusion complexes. CDs are cyclic oligosaccharides that have similar physiological and biological properties like linear saccharides of comparable molecular weight. Due to their very favorable toxicological and pharmacokinetic profiles their usage in parenteral drug formulations is frequently preferred over other solubilizing techniques. Here the physiochemical and biological properties of CDs are reviewed as well as their pharmacokinetics after intravenous administration. Their regulatory status is briefly reviewed and their tendency to self-assemble to form clusters or aggregates discussed. Finally, some examples are given of how CDs are applied in aqueous parenteral formulations, how their solubilizing effect has been enhanced and how their target concentration is determined.

Design, Synthesis, and Activity Study of Water-Soluble, Rapid-Release Propofol Prodrugs

In this work, a series of water-soluble propofol prodrugs were synthesized, and their propofol release rate and pharmacodynamic characteristics were measured. We found that inserting glycolic acid as a linker between propofol and the cyclic amino acid accelerated the release of propofol from prodrugs into the plasma while preserving its safety. In animal experiments, prodrugs (3e, 3g, and 3j) were significantly better than fospropofol (the only water-soluble propofol prodrug that has been used clinically) in terms of safety, onset, and duration time of anesthesia. Their molar dose, onset time, and anesthesia duration time were comparable to those of propofol, helping to maintain the clinical benefits of propofol. The experimental results showed the potential of such compounds as water-soluble prodrugs of propofol.

Sulfobutylether-β-cyclodextrin/5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphine nanoassemblies with sustained antimicrobial phototherapeutic action

Nowadays, novel less-expensive nanoformulations for in situ-controlled and safe delivery of photosensitisers (PSs) against opportunistic pathogens in body-infections areas need to be developed. Antimicrobial photodynamic therapy (aPDT) is a promising approach to treat bacterial infections that are recalcitrant to antibiotics. In this paper, we propose the design and characterization of a novel nanophototherapeutic based on the trade cyclodextrin CAPTISOL® (sulfobutylether-beta-cyclodextrin, SBE-βCD) and 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphine tetrakis(p-toluenesulfonate) (TMPyP) to fabricate efficient biocompatible systems for aPDT. Spherical nanoassemblies of about 360 nm based on CAPTISOL®/TMPyP supramolecular complexes with 1:1 stoichiometry and apparent equilibrium binding constant (K_b ≅ 1.32 × 10⁵ M^-1) were prepared with entrapment efficiency of ≅ 100% by simple mixing in aqueous media and freeze-drying. These systems have been characterized by complementary spectroscopy and microscopy techniques. Time resolved fluorescence pointed out the strong interaction of porphyrin monomer within nanoassemblies (τ₂ ≅ 11 ns with an amount of ca 90%) and scarce self-aggregation of porphyrins have been observed. Singlet oxygen comparative determination (ϕ_{Δ CAPTISOL}®_/TMPyP = 0.58) assessed their photodynamic potential. Release and photostability studies have been carried out under physiological conditions pointing out the role of CAPTISOL® to sustain porphyrin release for more than 2 weeks and to protect PS from photodegradation. Finally, photoantimicrobial activity of nanoassemblies vs free porphyrin have been investigated against Gram-negative P. aeruginosa, E. coli and Gram-positive S. aureus. The proposed nanosystems were able to photokill both Gram-positive and -negative bacterial cells similarly to TMPyP at MBC₉₀ = 6 µM of TMPyP and at 42 J/cm² light dose. However, with respect to the less selective free TMPyP in biological sites, nanoassemblies exhibit sustained release properties and a higher photostability thus optimizing the PDT effect at the site of action. These results can open routes for in vivo translational studies on nano(photo)drugs and nanotheranostics based on less expensive formulations of CD and PS.

Characterization, in Vivo Evaluation, and Molecular Modeling of Different Propofol-Cyclodextrin Complexes To Assess Their Drug Delivery Potential at the Blood-Brain Barrier Level

In this study, we investigated the ability of the general anesthetic propofol (PR) to form inclusion complexes with modified β-cyclodextrins, including sulfobutylether-β-cyclodextrin (SBEβCD) and hydroxypropyl-β-cyclodextrin (HPβCD). The PR/SBEβCD and PR/HPβCD complexes were prepared and characterized, and the blood-brain barrier (BBB) permeation potential of the formulated PR was examined in vivo for the purpose of controlled drug delivery. The PR/SBEβCD complex was found to be more stable in solution with a minimal degradation constant of 0.25 h^-1, a t_1/2 of 2.82 h, and a K_c of 5.19 × 10³ M^-1 and revealed higher BBB permeability rates compared with the reference substance (PR-LIPURO) considering the calculated brain-to-blood concentration ratio (logBB) values. Additionally, the diminished PR binding affinity to SBEβCD was confirmed in molecular dynamics simulations by a maximal Gibbs free energy of binding (ΔG_bind = -18.44 kcal·mol^-1), indicating the more rapid PR/SBEβCD dissociation. Overall, the results demonstrated that SBEβCD has the potential to be used as a prospective candidate for drug delivery vector development to improve the pharmacokinetic and pharmacodynamic properties of general anesthetic agents at the BBB level.

A Phase 1c Trial Comparing the Efficacy and Safety of a New Aqueous Formulation of Alphaxalone with Propofol

BACKGROUND:

Phaxan™ (PHAX, Chemic Labs, Canton, MA) is an aqueous solution of 10 mg/mL alphaxalone and 13% 7-sulfobutylether β-cyclodextrin (betadex). In preclinical studies, PHAX is a fast onset–offset IV anesthetic like propofol, but causes less cardiovascular depression. This first-in-man study was designed to find the anesthetic dose of PHAX and to compare it with an equivalent dose of propofol for safety, efficacy, and quality of recovery from anesthesia and sedation.

METHODS:

The study adhered to compliance with Good Clinical Practices regulations (clinical trials registry number, ACTRN12611000343909). This randomized, double-blind study compared PHAX and propofol using a Bayesian algorithm to determine dose equivalence for effects on the bispectral index (BIS). Male volunteers, ASA physical status I, gave written informed consent (n = 12 per group; PHAX or propofol). Parameters assessed for 80 minutes after drug injection (single bolus dose) were pain on injection, involuntary movement, BIS, blood pressure, need for airway support, and, as measures of recovery from sedation, the Richmond Agitation and Sedation Scale and the Digit Symbol Substitution Test. Arterial blood was withdrawn for biochemistry, hematology, and complement levels.

RESULTS:

No subject complained of pain on injection with PHAX, whereas 8 of the 12 subjects given propofol did. Nine PHAX and 8 propofol subjects reached BIS values of ≤50: median (interquartile range [IQR]) mg/kg dose = 0.5 (0.5–0.6) for PHAX and 2.9 (2.4–3.0) for propofol. The lowest median BIS reached was 27 to 28 for both agents with no significant differences between them for timing of onset and recovery of BIS. The concomitant median changes in systolic and diastolic blood pressures were −11% vs −19% for systolic and −25% vs −37% for diastolic in PHAX- and propofol-treated subjects, respectively. Nine of the 12 propofol-treated subjects and none of 12 PHAX-treated subjects required airway support. For subjects reaching an equivalent BIS of ≤50: a Richmond Agitation and Sedation Scale score of 0 was reached at a median of 5 (IQR, 5–10) and 15 (IQR, 10–20) minutes after PHAX and propofol, respectively; BIS returned to 90 at a mean of 21 (SD, 10.1) and 21 (SD, 9.2) minutes after PHAX and propofol, respectively; and Digit Symbol Substitution Test scores returned to predrug injection values at median of 50 (IQR, 35–72.5) and 42.5 (IQR, 35–76.3) minutes after PHAX and propofol, respectively. There was no increase in C3 and C4 complement fractions after either drug.

CONCLUSIONS:

PHAX causes fast-onset, short-duration anesthesia with fast cognitive recovery similar to propofol, but with less cardiovascular depression, or airway obstruction and no pain on injection.

Published ahead of print July 29, 2015

Pharmacokinetics of cyclodextrins and drugs after oral and parenteral administration of drug/cyclodextrin complexes

Objectives

The objective of the present study was to shed some light on pharmacokinetics of cyclodextrins (CDs) and drugs after oral and parenteral administration of inclusion complexes.

Key findings

The complex binding constant in water can predict pharmacokinetics after parenteral administration, but it has to be considered in the context of the physiological environment, where plasma proteins compete with CDs for drug binding. Neither drug/CD nor drug/protein complexes can extravasate, but differently from proteins, CDs are readily cleared through glomerular filtration. In such intricate interrelationships, for complexes with low-to-mid binding constant, binding of drug to plasma proteins will mainly dictate the pharmacokinetics. Oppositely, for drugs showing large CD complex binding constant and low protein binding, significant decrease in distribution volume and enhanced excretion of unmetabolized drug are observed; thus, relevant changes in bioavailability can be predicted. In the case of oral administration, volume for dilution/dissolution of the complexes is relatively low and hence excess CD can hamper drug absorption from the gastrointestinal (GI) tract.

Summary

CDs are well-established multipurpose excipients for overcoming organoleptic and biopharmaceutical deficiencies of a variety of drugs. Balances between free and complexed drug in the GI tract and between drug–CD binding and drug–protein binding in plasma seem to play a relevant role in drug pharmacokinetics.

Synthesis and evaluation of hydroponically alginate nanoparticles as novel carrier for intravenous delivery of propofol

Commercial lipid emulsion of propofol (CLE) has several drawbacks including pain on injection and emulsion instability. In this paper, a novel nanocarrier system is introduced to improve stability and solubility of the poorly soluble anesthetic drug, propofol, for intravenous administration. In this paper, alginate is modified using a facile method in which the carboxylic group of alginate is grafted to octanol. The octanol-grafted alginate (Alg-C8) is then employed to prepare nanoparticles which are subsequently used for encapsulation of propofol. The nanoparticles are analyzed for their pH, osmolarity, particle size, stability, morphology and sleep recovery and the results are compared with CLE as control. It is revealed that nanoparticles have the average particle size of 180 nm ± 1.2 and spherical morphology which is less than CLE while their pH, osmolarity and profile of release of formulated nanoparticles are similar to those of CLE. In addition, the results show good chemical and physical storage stability for the nanoparticles at room temperature for at least 6 months compared to CLE as control. The animal sleep recovery test on rats shows no significant difference in time of unconsciousness and recovery of the righting reflex between nanoparticles and CLE. It is concluded that encapsulated nanoparticles introduced here could be a promising clinical intravenous system for delivery of poorly soluble anesthetic propofol. In addition, this study provides an efficient and facile method for preparing a carrier system for water insoluble drugs.

New medications and techniques in ambulatory anesthesia

Novel anesthetic and analgesic agents are currently under development or investigation to improve anesthetic delivery and patient care. The pharmacokinetic and analgesic profiles of these agents are especially tailored to meet the challenges of rapid recovery and opioid minimization associated with ambulatory anesthesia practice.

Effects of propofol in lipid-based emulsion and in microemulsion on the incidence of endothelial lesion in rabbits

PURPOSE

To compare the incidence of endothelial injury after single-dose or continuous propofol infusion in conventional lipid-based emulsion (LE) versus microemulsion (ME).

METHODS

Forty-two rabbits (2.5-4.5 Kg) were randomly allocated into seven groups of six animals each: SHAM- surgical treatment alone; Bolus Control Group - 3 mL-intravenous (IV) bolus of saline; Continuous Infusion Control Group - 3 mL- IV bolus of saline followed by a continuous infusion of 0.2 ml/kg/min for 60 min; Bolus LE Propofol Group - IV bolus of LE propofol (3 mg/kg); Bolus ME Propofol Group - IV ME propofol bolus (3 mg/kg); Continuous LE Propofol Group - IV LE propofol bolus (3 mg/kg) followed by a continuous infusion of 0.2 ml/kg/min for 60 min; Continuous ME Propofol Group - IV ME propofol bolus (3 mg/kg) followed by a continuous infusion of 0.2 ml/kg/min for 60 min.

RESULTS

There were no statistically significant differences between the studied groups in blood pressure, in central venous pressure and in the biochemical profile. No significant differences were found in inflammatory mediators and in tissue analysis between the two emulsions.

CONCLUSION

Microemulsion and lipid-based emulsion propofol had similar inflammatory, biochemical and microscopy profiles. Thus, microemulsion propofol can be used as an alternative to lipid-based emulsion propofol.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Liquid chromatography-tandem mass spectroscopic method for the determination of zerumbone in human plasma and its application to pharmacokinetics

A rapid, sensitive, specific and selective LC-MS/MS method for the determination of zerumbone (ZER) in human plasma using 2,4-diamino-6-(4-methoxyphenyl)-1,3,5-triazine (DMTZ) as an internal standard (IS) has been developed and validated. ZER was chromatographed on C8 column using a mobile phase of acetonitrile/water (80:20, v/v) at a flow rate of 0.25 ml min(-1) . Quantitation was achieved using ESI+ interface, employing multiple reaction monitoring (MRM) mode at m/z 219 > 81 and 218 > 134 for ZER and IS, respectively. The calibration standards were linear over a range of 5-3000 ng ml(-1) (r(2)=0.9994) with an LLOQ of 5 ng ml(-1) (RSD %; 11.4% and bias%; 9.5%). Intra- and inter-day precision of ZER assay ranged from 0.18 to 3.56% with accuracy (bias) that varied between -5.09 and 4.3%, demonstrating good precision and accuracy. Recoveries of ZER and the IS from human plasma were above 85%. The developed method was validated for the determination of ZER in rat plasma. Linearity, stability of ZER and the ME on rat plasma were discussed. The applicability of the developed method was demonstrated by measuring ZER in rat plasma samples following intravenous and intraperitoneal administration of ZER prepared in hydroxypropyl-β-cyclodextrin (HPβCD) and sodium carboxymethyl cellulose (CMC), respectively, in 20 mg kg(-1) and this study indicated a clear significant difference (p<0.05) in pharmacokinetic parameters of ZER in ZER/HPβCD complex compared with ZER in CMC preparation.

Parenteral delivery of HPβCD: effects on drug-HSA binding

It is thought that cyclodextrins, such as 2-hydroxypropyl-β-cyclodextrin (HPβCD), will at high concentration affect pharmacokinetics of drugs through competitive binding with plasma proteins. Albumin is the major component of plasma proteins responsible for plasma protein binding. The purpose of this study was to evaluate in vitro the competitive binding of drugs between human serum albumin (HSA) and HPβCD in isotonic pH 7.4 phosphate buffer saline solution (PBS) at ambient temperature. Eight model drugs were selected based on their physicochemical properties and ability to form complexes with HSA and HPβCD. The drug/HPβCD stability constants (K(1:1)) were determined by the phase-solubility method and HSA/HPβCD competitive binding determined by an equilibrium dialysis method. Protein binding of drugs that are both strongly protein bound and have high affinity to HPβCD (i.e., have high K(1:1) value) is most likely to be affected by parenterally administered HPβCD. However, this in vitro study indicates that even for those drugs single parenteral dose of HPβCD has to be as high as 70 g to have detectable effect on their protein binding. Weakly protein bound drugs and drugs with low affinity towards HPβCD are insensitive to the cyclodextrin presence regardless their lipophilic properties.

Pharmaceutical applications of cyclodextrins: basic science and product development

Objectives

Drug pipelines are becoming increasingly difficult to formulate. This is punctuated by both retrospective and prospective analyses that show that while 40% of currently marketed drugs are poorly soluble based on the definition of the biopharmaceutical classification system (BCS), about 90% of drugs in development can be characterized as poorly soluble. Although a number of techniques have been suggested for increasing oral bioavailability and for enabling parenteral formulations, cyclodextrins have emerged as a productive approach. This short review is intended to provide both some basic science information as well as data on the ability to develop drugs in cyclodextrin-containing formulations.

Key findings

There are currently a number of marketed products that make use of these functional solubilizing excipients and new product introduction continues to demonstrate their high added value. The ability to predict whether cyclodextrins will be of benefit in creating a dosage form for a particular drug candidate requires a good working knowledge of the properties of cyclodextrins, their mechanism of solubilization and factors that contribute to, or detract from, the biopharmaceutical characteristics of the formed complexes.

Summary

We provide basic science information as well as data on the development of drugs in cyclodextrin-containing formulations. Cyclodextrins have emerged as an important tool in the formulator's armamentarium to improve apparent solubility and dissolution rate for poorly water-soluble drug candidates. The continued interest and productivity of these materials bode well for future application and their currency as excipients in research, development and drug product marketing.

Fospropofol disodium, a water-soluble prodrug of the intravenous anesthetic propofol (2,6-diisopropylphenol)

BACKGROUND

Today, propofol or 2,6-diisopropylphenol is the anesthetic mainly used for monitored anesthetic care sedation and during intravenous anesthesia. The formulation, a lipid macroemulsion, shows several disadvantages. Therefore, during the past years considerable scientific effort has been undertaken to find either a better formulation or a prodrug of propofol. Fospropofol is the first propofol prodrug that has been intensively studied in man. It has been licensed in 2008 by the FDA for monitored anesthetic care sedation.

OBJECTIVES AND METHODS

This review describes first published study results of fospropofol with regard to its pharmacokinetics/pharmacodynamics, drug safety, tolerability and drug side effects. Using a Medline search all published articles and abstracts containing the words fospropofol or GPI 15715 were included.

RESULTS AND CONCLUSION

As the impact of an errorness drug assay for propofol liberated from fospropofol is not exactly defined, no clear conclusions can be drawn from the first published pharmacokinetic/pharmacodynamic studies. Fospropofol was well tolerated in the first two clinical studies and no serious side effects were reported. After characterization of the true pharmacokinetic/pharmacodynamics profile, fospropofol, an aqueous solution, has the potential to favorably compare with benzodiazepines for procedural sedation and also may be used for long-term sedation and intravenous anesthesia.

Airway and systemic effects of soluble and suspension formulations of nebulized budesonide in asthmatic children

BACKGROUND

Using cyclodextrin with budesonide enables it to be formulated in a solution for nebulization.

OBJECTIVE

To observe the effects of a Captisol-enabled budesonide solution (CBIS), 60 microg twice daily, delivered via a nebulizer (eFlow), compared with a conventional budesonide suspension (Pulmicort Respules), 250 microg twice daily, delivered via another nebulizer (LC Plus), using fraction of exhaled nitric oxide (FE(NO)) and overnight urinary cortisol to creatinine ratio as the primary outcomes for efficacy and systemic bioactivity.

METHODS

A randomized, open-label, crossover study was conducted in 12 children with mild-to-moderate persistent asthma (aged 5-12 years). Measurements were performed after a 2-week steroid washout at baseline and at the end of each 2-week randomized treatment.

RESULTS

The nebulization time was shorter (95% confidence interval [CI], 0.83-5.63 minutes; P = .03) with CBIS (mean, 1.77 minutes) than with Pulmicort Respules (mean, 5.01 minutes). The reduction in FE(NO) with CBIS from pooled baseline was 2.45-fold (95% CI, 1.87-3.21; P < .001); and with Pulmicort Respules, 3.18-fold (95% CI, 2.26-4.47; P < .001). No statistically significant changes from pooled baseline in lung function and overnight urinary cortisol to creatinine ratio were observed with either treatment.

CONCLUSIONS

The nebulization time was shorter with CBIS compared with Pulmicort Respules. Both formulations exhibited similar anti-inflammatory activity in terms of reducing FE(NO), with no detectable difference between them when used in a putative microgram nominal dose ratio of 1:4. Neither formulation produced significant adrenal suppression.

Bioequivalence of 2 intravenous amiodarone formulations in healthy participants

Intravenous amiodarone is an effective agent for the treatment of recurrent ventricular fibrillation and hemodynamically unstable ventricular tachycardia. PM101 is a new formulation of intravenous amiodarone that uses a cyclodextrin to maintain amiodarone in the aqueous phase. Eighty-eight participants were enrolled in this randomized, double-blind, crossover, bioequivalence clinical study and were treated with single doses (150 mg) of PM101 and intravenous amiodarone separated by a washout period of at least 42 days. Venous blood samples were taken periodically during the first 72 hours after dosing to determine standard pharmacokinetic parameters. The amiodarone plasma concentration-time curve observed with both formulations was virtually identical, as was the 72-hour area under the curve (AUC0-72). Similar equivalence was seen for desethylamiodarone, the active metabolite of amiodarone. The geometric ratios of the AUC0-72 for amiodarone and desethylamiodarone were 1.03 (95% confidence interval [CI], 1.00-1.06) and 1.01 (0.99-1.03), respectively. Similar geometric ratios and CIs were found for maximum plasma concentration (Cmax) and for AUC extrapolated to infinity (AUC0-infinity). Because the ratios and their CI fell between the limits of 0.8 and 1.25, bioequivalence of these 2 formulations was established. No safety concerns unique to PM101 were identified.

PM101: a cyclodextrin-based intravenous formulation of amiodarone devoid of adverse hemodynamic effects

Intravenous amiodarone (Amiodarone i.v.) is widely used to treat cardiac arrhythmias. The most frequent clinical adverse event associated with Amiodarone i.v. administration is systemic hypotension which has been attributed to the cosolvents used in the formulation, polysorbate 80 and benzyl alcohol. To minimize hypotension Amiodarone i.v. is diluted in 5% dextrose in water prior to administration and slowly infused. PM101 is a novel intravenous formulation that uses sulfobutylether-7-beta-cyclodextrin to solubilize amiodarone, and thus should be devoid of the untoward hemodynamic effects associated with polysorbate 80 and benzyl alcohol. Beagle dogs (n=7/group) were anesthetized with morphine and alpha-chloralose and instrumented to assess aortic blood pressure, cardiac output, cardiac contractility, and heart rate. Animals were treated with the U.S. approved human-equivalent loading dose (2.14 mg/kg) of Amiodarone i.v., PM101, and their respective vehicle controls. Administration of Amiodarone i.v. rapidly and significantly decreased mean aortic pressure, cardiac output, and cardiac contractility. A significant increase in heart rate was also observed as was a transient, but not significant, decrease in systemic vascular resistance. A similar pattern of rapid and significant hemodynamic changes was produced by the Amiodarone i.v. Vehicle (polysorbate 80/benzyl alcohol) alone. In marked contrast, PM101 and its vehicle produced no significant hemodynamic effects. This study provides a useful model for the continued search for a safe and effective intravenous amiodarone formulation devoid of the hypotensive risk associated with the current commercial formulation.

The effects of pharmaceutical excipients on drug disposition

Many new chemical entities are poorly soluble, requiring the use of co-solvents or excipients to produce suitable intravenous formulations for early pre-clinical development studies. There is some evidence in the literature that these formulation components can have significant physiological and physicochemical effects which may alter the distribution and elimination of co-administered drugs. Such effects have the potential to influence the results of pre-clinical pharmacokinetic studies, giving a false impression of a compound's intrinsic pharmacokinetics and frustrating attempts to predict the drug's ultimate clinical pharmacokinetics. This review describes the reported effects of commonly used co-solvents and excipients on drug pharmacokinetics and on physiological systems which are likely to influence drug disposition. Such information will be useful in study design and evaluating data from pharmacokinetic experiments, so that the potential influence of formulation components can be minimised.

Neuromuscular monitoring and postoperative residual curarisation: a meta-analysis

We conducted a meta-analysis to examine the effect of intraoperative monitoring of neuromuscular function on the incidence of postoperative residual curarisation (PORC). PORC has been considered present when a patient has a train-of-four (TOF) ratio of < 0.7 or < 0.9. We analysed data from 24 trials (3375 patients) that were published between 1979 and 2005. We excluded data on mivacurium from this meta-analysis because only three studies had examined the incidence of PORC associated with its use. Long- and intermediate-acting neuromuscular blocking drugs had been given to 662 and 2713 patients, respectively. Neuromuscular function was monitored in 823 patients (24.4%). A simple peripheral nerve stimulator was used in 543 patients, and an objective monitor was used in 280. The incidence of PORC was found to be significantly lower after the use of intermediate neuromuscular blocking drugs. We could not demonstrate that the use of an intraoperative neuromuscular function monitor decreased the incidence of PORC.

Sugammadex: Another Milestone in Clinical Neuromuscular Pharmacology

Sugammadex is a revolutionary investigational reversal drug currently undergoing Phase III testing whose introduction into clinical practice may change the face of clinical neuromuscular pharmacology. A modified gamma-cyclodextrin, sugammadex exerts its effect by forming very tight water-soluble complexes at a 1:1 ratio with steroidal neuromuscular blocking drugs (rocuronium > vecuronium >> pancuronium). During rocuronium-induced neuromuscular blockade, the IV administration of sugammadex creates a concentration gradient favoring the movement of rocuronium molecules from the neuromuscular junction back into the plasma, which results in a fast recovery of neuromuscular function. Sugammadex is biologically inactive, does not bind to plasma proteins, and appears to be safe and well tolerated. Additionally, it has no effect on acetylcholinesterase or any receptor system in the body. The compound's efficacy as an antagonist does not appear to rely on renal excretion of the cyclodextrin-relaxant complex. Human and animal studies have demonstrated that sugammadex can reverse very deep neuromuscular blockade induced by rocuronium without muscle weakness. Its future clinical use should decrease the incidence of postoperative muscle weakness, and thus contribute to increased patient safety. Sugammadex will also facilitate the use of rocuronium for rapid sequence induction of anesthesia by providing a faster onset-offset profile than that seen with 1.0 mg/kg succinylcholine. Furthermore, no additional anticholinesterase or anticholinergic drugs would be needed for antagonism of residual neuromuscular blockade, which would mean the end of the cardiovascular and other side effects of these compounds. The clinical use of sugammadex promises to eliminate many of the shortcomings in our current practice with regard to the antagonism of rocuronium and possibly other steroidal neuromuscular blockers.

Drug development in anaesthesia: industrial perspective

PURPOSE OF REVIEW

In this review, we summarize the new drugs in development in the anaesthesia field.

RECENT FINDINGS

There are some interesting approaches, including pro-drugs of propofol such as Aquavan (MGI Pharma, Bloomington, Minnesota, USA) and novel 'soft-drug' sedatives and hypnotics (e.g. CNS-7259X and TD-4756) as well as a novel approach to terminate the action of steroidal neuromuscular blockers (sugammadex). There is also significant activity in the field of novel analgesics. Particularly addressing the fields of sedatives, hypnotics and neuromuscular blockers, however, there is relatively little drug discovery activity currently. Part of the reason for this may be that the mechanisms of action of anaesthetics are not fully understood. This cannot be the whole story, however, since attractive new targets have recently been identified. For example, an agent with selective actions at the beta3-containing subunit of the gamma-amino butyric acid-A receptor is likely to have the hypnotic effects of propofol without the cardiac depressant side-effects.

SUMMARY

We consider the main reason for low activity is the perception in industry that there is little need for new drugs in anaesthesia because the needs are well addressed by existing agents. If this is not the case then anaesthesiologists need to be more effective in communicating their requirements.

[Pharmacodynamics of two different propofol formulations]

BACKGROUND

Propofol is nowadays available in various lipid formulations. We compared two different propofol formulations with respect to pharmacodynamics, using the EEG and clinical signs.

MATERIALS AND METHODS

Ten volunteers received Diprivan 1% and Propofol 1% MCT Fresenius as a computer controlled infusion with increasing propofol target concentrations. A sigmoid E(max) model with effect compartment was estimated for the median frequency of the EEG power spectrum, based on measured arterial propofol plasma concentrations. Clinical pharmacodynamics were assessed by reaction on acoustic stimuli, eyelid reflex and corneal reflex.

RESULTS

The drugs did not differ in pharmacodynamics with respect to EEG (EC(50) 2.1+/-0.6 for Diprivan and 2.1+/-0.5 microg/ml for Propofol Fresenius) and clinical signs. The pharmacodynamic model was characterized by a steep concentration effect relationship and a distinct hysteresis between propofol plasma concentration and effect (k(e0) 0.12+/-0.04 and 0.12+/-0.5 min(-1)).

CONCLUSIONS

The investigated lipid formulations have no influence on the pharmacodynamics of propofol.

Cyclodextrins as new formulation entities and therapeutic agents

PURPOSE OF REVIEW

This review is focused on recent advances in the application of cyclodextrins to new drug formulations, with emphasis on the field of anesthesia.

RECENT FINDINGS

Cyclodextrins are well-known excipients in the pharmaceutical industry. Their recent application to the anesthetic induction agent propofol as a means of creating a non-lipid formulation may lead to their introduction into anesthesia pharmacology. The development of a novel cyclodextrin as specific reversal agent for the neuromuscular blocker rocuronium (that acts as an in-vivo scavenging system to bind free rocuronium in the circulation) will also increase the likelihood that cyclodextrins will have a greater clinical presence in anesthesiology in the future. Cyclodextrin-containing polymers are also finding a role in the delivery of nucleic acids and protein therapeutic agents.

SUMMARY

Recent developments in cyclodextrins as excipients for anesthetics may soon culminate in their introduction into anesthesiology, although more research is necessary to better define their potential.

Sedation with GPI 15715, a Water-Soluble Prodrug of Propofol, Using Target-Controlled Infusion in Volunteers: Retracted

GPI 15715 is the first water-soluble propofol prodrug that has been studied in humans. Present propofol lipid formulations have well known undesirable properties, for example, pain on injection and increased triglyceride concentrations. We investigated whether GPI 15715 is suitable to achieve and maintain moderate sedation for 2 h. Six male and six female volunteers received a target-controlled infusion of GPI 15715, with an initial propofol target concentration of 1.8 microg/mL and the possibility to adjust the propofol target once after 1 h. Propofol concentrations, the bispectral index, and modified Observer's Assessment of Alertness/Sedation Scale (MOAA/S) scores were monitored. The median MOAA/S score was 4 during the first hour and was 3 during the second hour of infusion. The propofol target had to be changed to 2.4 microg/mL in seven volunteers and to 3.0 microg/mL in two volunteers. A propofol concentration of 1.9 microg/mL had the highest probability to result in an MOAA/S score of 3, which corresponds with moderate sedation. We observed no serious side effects. We conclude that GPI 15715 produces excellent sedation.